We begin by defining the Atiyah bundle.
Let \(C\)  be a smooth projective curve.
Following
[1]},
for \(E\)  a vector bundle on \(C\) , define \(\operatorname{Diff}^1(E,E)\)  as follows: for
\(U\subset C\)  open, \(\operatorname{Diff}^1({E}, {E})(U)\)  is the set of
\(\mathbb {C}\) -linear endomorphisms \(\tau \)  of \(E(U)\) , such that for each \(f\in {O}_C(U), v\in E(U)\) , we have that
\(\tau _f: v\mapsto \tau (fv)-f\tau (v)\) 
